This invention relates to an electronic fuel injection system for an internal combustion engine, especially a system for absorbing pulsation of fuel pressure.
There is known an electronic fuel injection system for delivering an appropriate amount of fuel to an internal combustion engine. In the system, the fuel controlled, for example, at a pressure 2.55 Kg/cm.sup.2 higher than that at the intake manifold is supplied through an electro-magnetic valve, and the flow rate of the fuel is regulated by changing the width of an electric pulse transmitted to the electro-magnetic valve to alter the opening duration of the valve. Such a system is disclosed in many documents, such as SAE Paper No. 750,368, and is actually used on an automobile engine, such as of M-EU model (designation registered with the Japanese Ministry of Transportation) manufactured by the assignee company of this invention. The detailed construction of the engine is described in M-EU ENGINE REPAIR MANUAL published by TOYOTA MOTOR SALES CO., LTD. on Sept. 25, 1975, and its basic principles are already known to the public. As the electro-magnetic valve causes fuel to flow intermittently, the so-called "water hammer phenomenon" appears in the fuel pipe, bringing about pulsation of fuel pressure, undesirable fluctuations in the fuel-air ratio and abnormal noises. Therefore, the system is provided with a fuel damper in order to absorb the pulsation of fuel pressure.